This invention relates generally to energy conservation in buildings and, more particularly, has reference to the use of tracer gases to measure the infiltration of air into buildings.
There is a growing need to control energy loss in homes and commercial buildings. A substantial energy loss is caused by infiltration of cold air into heated buildings during the winter and infiltration of hot air into cooled buidlings during the summer. Using currently available methods, it is very difficult, time consuming, and costly to measure the amount of such infiltration and to locate the leakage points. It is especially difficult to establish an average leakage value over an extended period of time because the leakage rate changes substantially when weather or temperature changes occur. Most current methods require technicians to come to the building in question and make measurements over an extended period of time using complicated and expensive instruments.
The tracer dilution method is the most common method used today for infiltration rate measurement. It requires the release of a batch of tracer gas, usually sulfur hexafluoride. The gradual reduction in tracer gas concentration caused by air infiltration is measured at several precisely timed intervals. This technique is costly and its accuracy is dependent on the skill of the technician who applies it in the field.
In another technique, called the constant rate method, tracer gas is emitted continuously. The emission rate is varied to maintain a constant concentration of tracer gas in the building or in the room. The emission rate is recorded and used to calculate the infiltration rate according to the recorded emission rate and variations in the emission rate.